| Bluetooth is a very practical wireless communication technology, so that it is a very attractive choice to build a short-distance wireless ad hoc network. Piconet is the basic Bluetooth network. Several piconets connected in a certain way could form a scatternet, which could broaden more application scenarios. The point-to-point Bluetooth audio transmission can’t meet the increased needs, so the research and development of Bluetooth audio product is still an issue, the research difficulties is how to connect an audio source device to multiple audio receiving devices by Bluetooth wireless communication, and the synchronization of multiple receiving devices when streaming.In this paper, we combine the issues of Bluetooth scatternet and audio transmission, research and design how to apply the theory of Bluetooth scatternet to audio transmission to implement Bluetooth audio transmission system with larger coverage range and longer transmission distance.The main research works of this paper are as follows:by studying Bluetooth audio protocols, application profiles and the key issues of Bluetooth scatternet in audio transmission applications, presented a Bluetooth audio application profile based on ACL link, proposed the chain tree scatternet topology which is simpler to form and easier to achieve, designed the working scheme of the chain tree topology in the audio transmission scenario, chose SBC codec technology which is suitable for the chain tree scatternet audio transmission application, analyzed the issue for synchronous playback of multiple audio streams in the network, and according to the decoding processing delay of each piconet and the sensitivity of the human ear, calculated the maximum quantity of piconets the chain tree scatternet could connect.Then on the base of theoretical research, this paper developed and implemented the Bluetooth scatternet audio transmission system:first we deeply studied the working principle of CSR8670 chip development board and its supporting software platform, designed hardware developing structure of the relay Bluetooth device and the sink Bluetooth device; then mainly designed and developed state module, inquiry module, DSP module, button and LED module of the system by means of software development platform, realized the successful connect of the audio source Bluetooth device, the relay Bluetooth device and the sink Bluetooth device, and the synchronous playback of the relay device and the sink device. Finally we realized the chain tree Bluetooth scatternet audio transmission system with three devices. |
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